This application claims the priority of Korean Patent Application No. 2002-63853 filed on Oct. 18, 2002 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an MEMS (micro-electro-mechanical system) actuator and a method of manufacturing the same, and more particularly, to a 2-D MEMS actuator and a method of manufacturing the same.
2. Description of the Related Art
An MEMS actuator applied to an optical scanner includes a micro-mirror that moves in one direction or two directions by an electrostatic force.
U.S. Pat. No. 5,025,346 discloses a microactuator using an electrostatic effect obtained by a comb-typed electrode. The microactuator has a structure in which a movable comb electrode and a stationary comb electrode are alternately arranged at a movable structure and a stationary structure. The movable structure is suspended by a nearby support structure. The suspended structure is driven at a horizontal resonant frequency.
The conventional microactuator has a structure in which a driving movable comb electrode is formed parallel to a plane of a stage or a movable structure, and a stationary comb electrode corresponding to the driving comb electrode is alternately arranged with the driving comb electrode in a fixed state and parallel to a plane direction of the stage, like the driving comb electrode. In the conventional microactuator, since the comb electrode is provided around the stage, the overall size of the microactuator considerably increases compared to the stage or movable structure. As a result, the conventional actuator is limited in its application.
In the meantime, a bi-axes driving actuator having a structure in which one axis driving structure is supported by a second seesaw mechanical structure has been suggested (Harald Schenk, Sensors and Actuators A 89 (2001), pp. 104–111, and IEEE Journal of Selected Topics in Quantum Electronics, vol. 6, no. 5 (2000) pp. 715–722).
The bi-axes driving actuator is an extended application of one axis driving actuator and has a structure in which a stationary comb electrode and a driving comb electrode to drive a first axis and a stationary comb electrode and a driving comb electrode to drive a second axis are all disposed on a plane. Thus, the arrangement structure of the comb electrodes as in the first axis driving actuator greatly limits an effective area of a stage for optical scanning. Also, since the above bi-axes driving actuator is a resonant scanner which moves continuously, a static mirror positioning is not possible so that a linear driving is impossible.
Also, since the driving comb electrode and the stationary comb electrode are arranged on a plane such as a stage or a frame, a symmetrical electric field is generated between the driving comb electrode and the stationary comb electrode so that a driving force to induce driving of the stage cannot be obtained. Therefore, an additional starting electrode to generate asymmetrical electric field is needed for driving the stage. Also, since one stage is provided at one scanner, the bi-axes driving actuator is difficult to be applied to a laser television requiring a reflection surface of a sufficient size. Although it is need to arrange a plurality of mirror plates in an array form for a driving speed of 10 KHz or more required in a laser television while having a sufficient reflection surface over 1×1 mm2, a plurality of mirror plates cannot be arranged in the scanner suggested by Harald Schenk.